The invention relates generally to a junction or joint for sheet-like material and, more particularly, to a manner of effecting a connection between overlapping sections of sheet-like material. Of special interest is a band for lifting heavy loads which is made from a strip of material such as steel which has been formed into the shape of a closed loop with the ends of the strip overlapping one another.
The term "sheet-like" or "sheet" as used herein is intended to encompass foils, strips, sheets, webs and the like.
Lifting bands, that is, bands for lifting loads, are used in the transport of elongated material sections such as, for example, steel bars, or rods, which are bound together into the form of bundles by means of wires, for instance, and are transported by a crane or the like. The lifting bands are usually maintained in position about the bundles of goods until these have arrived at their final destination. This eliminates the necessity for providing additional chains or the like for conveying the goods when the latter are transferred from one transporting device to another or when the goods must be moved around internally within the warehouse. Moreover, by maintaining the lifting bands in position about the goods, the work of the person transporting the goods is simplified since the jockeying and experimentation which would otherwise be required to engage the hooks of the crane or transporting device to the wires or other elements which bind the individual material sections into a bundle are greatly reduced.
It is known to make lifting bands for this purpose by forming a steel strip into the form of a closed loop or band with the ends of the strip overlapping one another. The overlapping ends of the strip are then connected to each other by means of electric spot welding. These lifting bands have the disadvantage that they must have large cross-sections if they are to be used for heavy loads. The reason is that they must be made of a steel having a low carbon content and, consequently, low strength, if they are to be spot weldable.
Lifting bands having large cross-sections are unwieldy and are also expensive because of the large quantities of material required to make them. Furthermore, the quality of the spot welds is dependent upon the metallurgical quality and condition of the material used, upon the quality and condition of the surface of the strip and upon the welding apparatus utilized. As a result, it is only possible to obtain an approximate relationship between the breaking load of the material of the band and the breaking load of the connection between the ends of the strip from which the band is made. In other words, the ratio of the strength of the connection to the strength of the material of the band will vary from case to case and will not be constant.